a(n) = n*(25*n - 1)/2.

Terms

a(0) =0a(1) =12a(2) =49a(3) =111a(4) =198a(5) =310a(6) =447a(7) =609a(8) =796a(9) =1008a(10) =1245a(11) =1507a(12) =1794a(13) =2106a(14) =2443a(15) =2805a(16) =3192a(17) =3604a(18) =4041a(19) =4503a(20) =4990a(21) =5502a(22) =6039a(23) =6601a(24) =7188a(25) =7800a(26) =8437a(27) =9099a(28) =9786a(29) =10498